A known cable of this type is shown in FIGS. 7 and 8. It consists essentially of conductive wire 1 having a circular cross section and insulating sheath 2 covering wire 1. When this cable is pressed into slit 3a in cramping terminal 3, edges of slit 3a penetrate insulating sheath 2 and linearly cut into the outer portion of conductive wire 1, thereby making electrical contact therewith.
In such a structure, if the contact area between wire 1 and slit 3a is smaller than the cross section of wire 1, the electrical resistance of the contact portion is larger than that of wire 1. This is not desirable because it causes local generation of heat. Considering the thickness of the plate forming cramping terminal 3, the diameter of conductive wire 1, the rate of deformation of the conductive wire as it is pressed into the slit, as well as other factors, width W of slit 3a of terminal 3 is such that the contact area between conductive wire 1 and cramping terminal 3 is larger than the cross section of conductive wire 1. To accomplish this, width W must be considerably smaller than the diameter of conductive wire 1. Particularly, when a thick conductive wire 1 is used, the lateral edges of slit 3a cut more deeply into the outer portion of conductive wire 1. Thus, a greater pressing force is required, making the cable pressing operation more difficult.
Comparing an electrical wiring using the cables and the cramping terminals of this type with a busbar type wiring using conductive plates as conductors, the temperature of the conductors increases to a greater extent in the former wiring, thereby necessitating measures to cope therewith. The temperature increase is greater in the former case because the surface area of the conductive wire having a circular cross section is smaller than that of the busbar having a rectangular cross section, provided, of course, that both cross sections have the same total area.